Programming control system



O. LIVINGSTON ETAL PROGRAMMING CONTROL SYSTEM Jan. 9, 1951 Filed Feb. 17, 1949 v., ...Ca e see n .QP .r @.mR.. o .n.we t nLc t wh A e ,mhp .m Fm M WL w1 Haus.: Qn

Jan. 9, 1951 o. w. LIVINGSTON Erm. Y .2,537,770

l PROGRAMMING CONTRQL SYSTEI Filed Feb. 17. 1949 F` r2.2. Fig. 5.

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Inventors: Orrin W. Livingston, Lawrence R. peaslee,

13% ,3f/)hm heir Attorney.

Juif 9, 1951 o. w. LIVINGSTON Erm. 2,537,770

PROGRAMMING CONTROL SYSTEM 3 Sheets-Sheet 3 Filed Feb. 17. 1949 llll Il 400 CYCLE SELSYN EXS'LE Pig.

CROSSFEED 0R LONGITUDINAL AHPLIDYNE FIELD AMPLlFIER Figlo. D C OUTPUT DISCRHINATORl Patented Jan. 9, 1951 PROGRAMMING CONTROL SYSTEM Orrin W. Livingston, Scotia,

Peaslee, Schenectady,

-cral Electric Company,

York

and Lawrence R.

N. Y., assignors to Gena corporation of New Application February 17, 1949, Serial No. 76,888

4 Claims.

vThis invention relates to control systems, more particularly to control systems for controlling machines or processes in vwhich a program or sequence is repeatedmany times and an object of the invention is the provision of a simple, reliable and improved control system of this character. v

More specilca'ly, the invention relates to systems for controlling a program of sequential operations and a further object of the invention is the provision of a simple and c iiicient system for recording a program of motion, speeds, positions or other variable quantities or characteristics and for subsequently playing back the recording and causing the recordedvprcgram to reproduce the original sequence of operations with a high degree of accuracy.

In carrying theninvention into effect in one form thereof a reference pulsating voltage is recorded ona suitable record. A load device, of which `the position, movement, speed or other operating characteristic is to be controlled, is driven by a suitable driving means. 'Ihe rotor member of a rotary induction device is coupled to be rotated with respect to its stator member in response to movement of the load device. lInstator and rotor members. To one of these windwhich is obtained from the source of reference voltage. 'I'he other winding is connected to the record a ypulsating control voltage of which the voltage varies in response to movement of the load device. On'the playback to reproduce the original movement of the load device, the recorded reference voltage' and control voltage are reproduced The reproduced reference voltage is supplied to one winding of the rotary induction device. The `other winding of this device is condiscriminator. VTo a second input circuit of the phase discrimin'ator is supplied the reproduced control voltage. 'Any change in the phase relationship of these two input circuit voltages manifests itself at the output terminals as a divariations in the the polarity changes with opposite departures from a predetermined phase relationship. This direct voltage is utilized to control the driving means to move the load device and simultaneously to rotate the rotor of the vinduction device in a direction to restore the predetermined .phase ductivefy related lwindings are mounted Aon thev ings is supplied a periodically varying Voltage recording headl so that there is recorded on the riected to oneinput circuit of an electronic phaserect voltage of which the magnitude varies with,

phase relationship and oi which phase relationship with respect to the reference relationship of the voltages supplied to the input circuit of the discriminator.

For abetter and more complete understanding of the invention, reference should now be had to the following specification and to the accompanying drawing, of which Fig. 1 is a block diagram 'of a record-playback systemapplied to the control of a production lathe; Fig. 2 is a simple schematic diagram ofa bias oscillator for use during recording; Fig. 3 is a simpe schematic diagram of a relatively low frequency oscillator from which all reference and position-signal voltages are obtained during the recording operation;

.diagramof an electronic amplifier for amplifying the direct voltage at the voutput of the discriminator and supplying the amplified voltage to control the driving means for the load device; Fig. 9 is a schematic diagram of an electronic exciter and amplifier unit for converting single phase voltages to three phase voltages and supplying the three phase voltages to the rotary induction device;` and Fig. 10 is a curve which ,facilitates an understanding of the operation of the phase discriminator. l

Referring now to the drawing, a production lathe l 'has a longitudinal feed lead screw 2 and a cross-feed lead screw 3. A workpiece 4 is supported in the usual manner between centers in the head stock and the tail stock and isl engaged by a cutting tool 5 which is mounted in a rest on the'cross-feed slide 6.

The longitudinal lead screw 2v is kdriven by suitable driving means a direct current motor 1. feed lead screw 3 is driven means which is illustrated motor 8.

` For the purpose of voltage of which the phase with respect to the reference voltage varies in response to the movement of the carriage 9, a-rotaryinduction device I0 isl provided. is physically'similar to a wound rotor induction motor. It has a rotor member which` is mechanically coupledl to the longitudinal lead screw 2 Similarly the. crossby suitable driving as a direct current which is illustrated as providing an alternating This device is a Se'syn which and a stator member. A three phase distributed winding (not shown) is mounted on the stator member and an inductively related single phase winding is mounted on theY rotor member. This arrangement may be reversed if desired. The rotor member of a similar rotary induction device Il is mechanically coupled to the cross field lead screw 3. i

During the recording operation a three phase alternating voltage is supplied to the three phase primary windings of rotary induction devices III and II from a Selsyn exciter and amplifier unit I2 which in turn is supplied from an oscillator I3. Although the oscillator I3 may be of any suitable type it is preferred to utilize the electronic oscillator of which the circuits are illustrated in detail in Fig. 3. It is a well known conventional type of oscillator and is described as a resistance-capacitance coupled oscillator. Inductance I4 and capacitor I5 in the anode circuit of the oscillator valve provide a degree of tuning in the anode circuit and the capacitors I1 and vresistors I8 in the grid circuit produce a 180 degree shift in the phase of the grid voltage with respect to the anode voltage. Preferably the grid and anode circuits are tuned for oscillation at a relatively low frequency, e. g. 400 cycles. A direct voltage of suitable magnitude is supplied to the anode-cathode circuit of the oscillator valve I between the conductor I9 and ground 20. This direct voltage is maintained substantially constant by means of a voltage regulator valve 2I.

An oscillating voltage is supplied from the junction point of the potentiometer 22 and resistor I8 to the grid circuit of an electric valve 23 which is connected to operate as a cathode follower. the cathode circuit. The cathode follower valve 23 reproduces the oscillations of the oscillator valve across the potentiometer 24. The oscillating voltage between the slider 24a and the ground is supplied to the input circuit of the selsyn exciter amplifier unit I2.

This amplier unit comprises two power amplifiers. One of these power amplifiers is illustrated within the dotted enclosure I2a of Fig. 9 and the other is shown within the dotted enclosure l2b. The input to the entire amplifier unit is supplied across the gain potentiometer 25, to the slider 25a of which is connected the control grid 25a of an electric valve 25 which constitutes a single stage amplifier. A capacitor 21 and a gain potentiometer 28 are connected in series from the anode of valve 25 to ground, which is the negative terminal of a direct voltage supply source of which the conductor I2c represents the positive terminal. From the slider 28a of potentiometer 28, the output of the first stage amplifier valve is supplied to the input of the power amplier within the dotted enclosure l2b, which is illustrated as comprising both sections of a twin triode electric valve 29 and a beam power tube all connected in cascade. The output of the beam power tube 30 is supplied to one primary winding 3 la of a Scott connected transformer.

The `power amplifier within the dotted enclosure I2a also comprises both sections of a twin triode electric valve 32 and a beam power tube 33 connected in cascade. From the junction point of capacitor 21 and potentiometer 23, the outputof the first stage valve is fed through a resistor 34 and a potentiometer 35 to the control grid 32a'of the first section of the twin triode valve 32. The resistor 34. potentiometer 35 and capacitors 35 and 31 constitute a phase shift net- A potentiometer 24 is connected in work to produce a degree phase shift of the input voltage and consequently a 90 degree phase shift of the output voltage which is supplied to the quadrature primary winding 3Ib of the Scott transformer. Since no phase shift network is provided in the input circuit of the power amplifier within the dotted enclosure I2b, its output voltage which is supplied to the primary winding 3 Ia of the Scott transformer has zero phase shift. Since the voltages which are supplied to the primary windings 3Ia and 3Ib are 90 degrees out of phase, a balanced three phase voltage appears at' the secondary terminals 3Ic, 3Id and 3Ie, and this three phase voltage is supplied to the primary windings of the rotary induction devices l and 3 to which the secondary of the Scott transformer is connected by means of conductors 38.

During recording it is desirable to supply to the recording head coils a voltage of relatively high frequency, e. g. 30,000 cycles. Owing to its relative high frequency, this voltage is not recorded. Its purpose is to overcome the effect of hysteresis in the magnetic layer of the tape and thusto assure linear reproduction of the lower frequency voltages which are recorded. This high frequency bias voltage is obtained from` a suitable source, such as the oscillator 39 illustrated in Fig. 2. This oscillator comprises one section of a twin triode electric valve 40 used as an oscillator valve and the other section of the twin triode which is connected to operate as an amplifier. In the anode circuit of the oscillator section is connected a resistor and across the anode and cathode a capacitor 4I and a resistor 42 are connected in series. From the junction point of capacitor 4I and resistor 42 the output of the oscillator section is supplied to the grid of the amplifier section. The anode of this section and ground constitute the output terminals. A resistor 40a in the cathode circuit of the amplier section produces degeneration which improves the stability of the amplifier.

The output is supplied to a record circuit 43 in which it is mixed with the low frequency reference voltage which is supplied from the low frequency oscillator I3. As shown in Fig. 4, this record circuit comprises a'transforxner having a primary winding 44a and a secondary winding 44h. One terminal of the primary winding is connected directly to ground and the other terminal is connected through conductor 45 and the contacts of a record-play switch to the output of the low frequency oscillator I3. One terminal of the secondary winding 44b is connected through a capacitor 46 and conductor 41 to the anode output terminal of the bias oscillator 33. This terminal is also connected through a reactance 48 to ground and the opposite terminal is connected through conductor 49 and contacts of a record-play switch to one terminal of the recording head coil 5l), the other terminal of which is grounded. Thus there is supplied to the coil 50 an alternating voltage having a 30,000 cycle component and a 400 cycle component. The 400 cycle component is recorded as a reference voltage.

The single phase secondary winding of the rotary induction device I0 is connected through a conductor 5I and the contacts of a record-plai1 switch to a record circuit 52 in which the low frequency voltage induced in the secondary winding of the rotary induction device is mixed with a high frequency voltage obtained from the bias oscillator 39. This mixed alternating voltage is supplied through the output conductor 53 and contacts of' a record-play switch to the recording head coil 54 and the low frequency component of the mixed voltage is recorded on the tape. Similarly the single phase secondary winding of the rotary induction device Il is connected through a conductor 55 and contacts of a recordplay switch to a record circuit 56 in which the frequency secondary voltage of the rotary induction device is mixed with a high frequency voltage obtained from the bias oscillator 39. The mixedvolta'ge is supplied through conductor 51 and contacts of a record-play switch to the recording head coil 58, and the low frequency component is recorded on the tape. The record circuits 52 and 56 are identical with the record circuit 43 and therefore a description of them is omitted. i*

During the' playback operation the voltage reproduced by the record-playback head coil 54 is compared with the secondary voltage of rotary induction device i and any variation in the phase relationship of the two voltages is utilized to control the direct current motor 1 which drives the f longitudinal lead screw 2.

To detect variations in phase relationship of these two voltages, a phase discriminator 59 is provided. It is illustrated in Fig. 6. Ihis dis- The valve 60 amplies the voltage reproduced in the coil 54 and the amplified voltage which appears across the two anodes 60a and 60h is supplied through the transformer 64 to the grids of discriminator valves 62 and 63. The single phase voltage which is supplied from the rotary induction device I0 through conductor 5I and the playback contacts of a record-play switch during playback is amplified by the valve 6I and the amplifled voltage which appears across the anodes l6Ia and Bib is supplied through transformers 65 and 66 to the anodes of the discriminator valves 62 and 63. In operation, if .the input voltages to the amplifiers are exactly in phase then the voltages supplied to anode 62a and grid 62e will be in phase and similarly the voltages supplied to anode 63a and grid 63e will be in phase and consequently a direct voltage will appear across resistor '61 which is positive at the cathode end. Owing to the polarity of the transformer connections the voltages of the anodes 62h and 63h will be 180 degrees out of phase with the voltages of the grids 62d and 63d, respectively, and the Voltage across the resistor 68 will be zero. Thus the voltage across the resistor 61 constitutes the output voltage between the conductor 69 and ground. Under the conditions assumed, the output voltage will be maximum and positive at the conductor 69. Similarly when the input voltages to the amplifier are 180 degrees out of phase, the voltages of anodes B2b and 63h will be in-phase with the voltages of grids 62d and 63d, respectively, and a direct voltage will appear across resistor 68. The magnitude of this voltage will be maximum and its polarity will be positive at the cathode end of the resistor. The voltages of anodes 62a and 63a will conductor 69 will be negative. If the input volt# ages supplied to the amplifiers are 90 degrees out of phase, the direct voltages across the resistors 61 and 68 will be equal and opposite and the output voltage between conductor 69 and ground will therefore be zero. Thus for inphase input voltages the output voltage is maximum and positive at conductors 69. With the input voltage to amplifier valve 6| lagging the input voltage to amplifier valve 62 90 degrees, the output voltage will be zero, and for a. 180 degree lagging phase displacement of the input voltages the output is maximum and negative at the conductor 69. For intermediate phase relationships between inphase and 90 degree lagging, the output voltage has corresponding intermediate values and is positive at conductor 69. For intermediate phase relationships between 90 degrees lagging and 180 degrees lagging, the output voltage has corresponding intermediate values and its polarity is negative at the conductor 69. These relationships are illustrated graphically in Fig. 10 in which ordinates of the curve 10 represent the voltage at the output conductor 69 and the zero axis represents ground voltage which is zero. Ordinates above the zero axis represent positive values of voltage at conductor 69 and ordinates below the zero axis represent negative voltages at conductor 69.

The output voltage is amplified by means of a suitable electronic amplifier 1I. It is illustrated in Fig. 8 as a two-stage ampliflerof which the first stage comprises a twin triode valve 1|a with cathode coupling between the two sections of the valve and the second stage comprises the two beam power tubes 12 and 13 with cathode coupling. Resistors 14 and 15 are connected in the anode circuits of the valves 12 and 13 and the voltage across each of the resistors constitutes the output voltage for the corresponding valve. These output voltages are supplied to the control field windings 16a and 16h of a suitable dynamoelectric machine, such as the amplidyne 16. 'Ihe various grid biases of the valves of amplifier 1I are so chosen that with zero output voltage supplied to the input of the first stage, the two second stage valves will be conducting approximately equal values of current in approximately midrange. Consequenly the control fields 16a and 16h of the amplidyne will be equally and oppositely energized; \the net excitation will be zero and the voltage at the load axis brushes 16e and 16d will be zero. When the voltage supplied to the input of the first stage valve is maximum and positive, the current conducted by power valve 12 will decrease and the current conducted by power valve 13 will increase correspondingly. Consequently the current supplied to the control eld 16h' will be increased to a maximum and the current supplied to control field 16a Will be correspondingly decreased thereby to produce a maximum net excitation of the amplidynev and a maximum output voltage which may be assumed to be positive at load brush 16C.` Similarly when the voltage supplied to the input of the first stage valve is maximum and negative at the conductor 69a, the voltage at the load axis brushes will be maximum but of reverse polarity. The load axis brushes of amplidyne 16 are connected to the arhowever be 180 degrees out of phase with the the output voltage and its polarity at the output mature of the longitudinal feed motor- 1.

A phase discriminator 11, which is in all respects identical with the phase discriminator 59, is provided for producing a direct control voltage during playback in response to variations in phase between the voltage induced in the sec-` that the voltage of the ondary single phase winding of rotary induction device I I and the voltage induced in the recordlng and playback head coil 58. This control voltage is amplified by means of an amplifier 18 which is in all respects identical with the amplier 1|. From the output circuit of amplifier 18 voltages are supplied to the control field windings 19a and 19D of an amplidyne 18. The load axis brush voltage of amplidyne 19 is supplied to the D.-C. motor 8 which drives the cross-feed lead screw 3.

Between the reference voltage record and playback head coil 50 and the input to the amplifier unit I2 is connected a preamplifier unit 89 which is used during the playback operation. It is illustrated conventionally in Fig. l and in detail in Fig. 5. Preferably it is a two-stage amplifier of which the first stage comprises one section of a twin triode electric valve 8I and the second stage comprises the second section of the valve with capacitative coupling between the two secl tions. The voltage induced in the coil 50 during playback is supplied through contacts of a record and playback switch to the input circuit between the grid 8Ia and ground of the first section of the valve and during playback to the output is supplied from the anode 8Ib of the record section of the valve through vcontacts of a record and playback switch to the input of the exciter` amplifier unit I2. Similar preamplifier units 82 and 83 are connected between the record and .payback head coils 58 and 54 and corresponding input circuits of the cross-feed and longitudinal phase discriminators 11 and 59, respectively.

For the purpose of controlling the operation of the machine tool by hand, a suitable master control station 84 is provided. As shown in Fig. 1, it comprises a pair of potentiometers 85 and 85 which are connected across a source of direct voltage which is representedby the supply lines 81 and 81a. The midpoint of each of the potentiometer resistors is grounded. Assuming supply lines 81 and 81a is 21') volts and that the supply line 81 is positive, the voltage of line 81 will be 105 volts positive and the voltage of the line 81a will be 105 volts negative with respect to the grounded midtaps. By moving the sliders 85a and 86a .to one side or the other of the grounded midtaps, direct voltage signals, reversible in polarity and variable in magnitude, dependent on the potentiometer settings, are supplied to the input circuits of the amplidyne field amplifiers 1B and 1I. As a resut, the feed motors 8 and 1 will rotate to position the tool. in a direction corresponding to the direction of displacement of the corresponding slider from neutral and at a speed corresponding to the amount of the displacement.

The magnetic recorder is similar in principle to those widely used in the radio broadcast and entertainment fields. The multiple channel magnetic tape 88 is wound upon a storage or unwinding reel 89. Its outer end is threaded through the recording and playback head and attached to the drum of the winding reel 90. The winding-up reel is driven by suitable driving means, such as an electric motor (not shown) and tension is maintained in the tape by means of an electric motor coupled to the unwinding reel 89 and driven thereby as a generator to provide regenerative braking. Usually a caostan is mounted between the take-up reel and the recording head and the tape passes between the drum of the capstan and a pinch roll. The capstan is Each of the motors will rotate driven at a speed which is substantially constant by suitable driving means, such as an induction mOQX- '.'Lhe driving motors for the reels and capstan constitute no part of the present invention and consequentiy they are omitted from the drawing in the interest of simplicity. It is sufficient for the purposes of the invention to understand that during the recording and playback operations the tape is drawn past the recording head at substantially constant speed. Between the two operations the tape is rewound on the storage reel 89.

With the foregoing understanding of the elements and their organization in the complete system. the operation of the system itself will readily be understood from the following description.

In operation, the operator chucks his stock workpiece 4 and operates the record-playback switch 9| to the recordJposition, i. e. to the posiv y l tion illustrated in Fig. 1, in which all the movable contacts engage the upper stationary contacts R.

`The tool is positioned to a known zero point or reference point. This is accomplished .with the assistance of the usual micrometer dials with which the lathe is provided. The movement of the tool to the reference point is effected by using the speed control potentlometers and 86 of the master control station 84. Movement of the slider 85a to the left of its neutral position causes a positive voltage to be supplied to the input circuit of the cross-feed amplidyne field amplifier 19, which in turn supplies the amplified signal to the control field windings 19a, and 19h of the tool back from the work, the slider 85a is moved to the right of its neutral position so that a negative voltage is supplied to the input circuit of the amplifier 18. This causes the ampliiler to reverse the relative excitations of the control field windings of the ampldyne, thereby reversing the polarity of its net excitation. A voltage of reverse polarity is supplied to the armature of the motor 8, causing it to rotate in the reverse direction to withdraw the tool from the work. The longitudinal feed is controlled in a similar manner.

Once the tool is located the recorder is turned on begins to move past the record and playback head coils 59, 54 and 58. A 400 cycle signal voltage from the oscillator I3 is supplied through the record contacts to the record circuit 43. In this circuit it is reduced in magnitude and mixed with the 30,000 cycle bias voltage. The resulting signal voltage is supplied through conductor 49 and contacts of the record switch to the coil 50 of the recording head. This causes a track of magnetic signals to be induced on the tape. As previously explained, the 30,000 cycle component of the signal is not recorded owing to its high frequency. The 400 cycle component, which serves as a reference signal, is recorded.

A 400 cycle signal voltage from the oscillator I3 is also supplied through the contacts of the record switch to the Selsyn exciter amplifler unit I2. The three phase output voltage of this unit is supplied to the stator windings of the crossat the reference point, and the magnetic tape feedv and longitudinal feed .rotary inductiondevices Hand IIJ, respectively.

j marmo 'I'he phase of the singleV phase voltage in- `duced in the rotor winding of the cross-feed rotary induction device with respect to the referr ence voltage being? recorded on the tape Arepresents the position of the cross-feed and thus rep-v, resents the position of the tool on the cross-feed` axis. This single phase rotor voltage is supplied Vthrough conductor 55 and contacts oi? the record switch to the record circuit 56. In this vdeio t r ins voltage. This pattern of phase relationship represents the instant to instant position of the tool on the axis of the cross-feed.

Y When the turning operation is completed, the t `tool is returned to the zero or reference position rin which it was located at the beginning of the recorded operations. The tape 88 is rewound on the storage reel and the switch 9| is moved to the playbackposition.l The turned workpiece is replaced in the lathe by a piece of stock and the recorder is turnedl on and the tape is again drawn vice it is reduced in magnitude and mixed with ponent is recorded on the tape. Thus there isf. recorded on the tape asignal voltage of which the phase with respect to the reference voltage represents the position of the tool along the cross-ileld. f 'v v In asimilar manner positionsignals from the longitudinal freed rotary induction devicek I0 are supplied through conductor 5| to the record circuit 52 and mixed with the 30,000 bias voltage. Theresulting signal yis supplied to the coil 54 and the 400 cycle component is recorded on the tape. l

The workpiece may now be turned to the desiredV shape by manipulating the potentiometers 85 and 86 of the master control station 84, as explained in the foregoing. Alternatively, an automatic contouring control system, such as disclosed in -Patent 2,410,295-11 P. Kuehi et al., may be utilized to follow the outline of a pattern and control the motors 8 and 1 to position the tool to reproduce the pattern.

Thus while the work is being continuously turned, the longitudinal and cross-feed positions are being recorded. Simultaneously the reference voltage signal is being recorded.

If the longitudinal feed is stationary, thephase of the signal voltagerecorded on the tape by the coil 54 will not Achange with respect to the reference voltage slgnalrecorded bythe coil 50.

This constant relationship of the phase of the recorded longitudinal feed signal voltage and the recorded reference signal voltage continues as long as the longitudinal feed is stationary.v If during a succeeding instant of time the longitudinal feed moves a predetermined amount, vthe rotor ofthe rotaryinduction device i0 `is rotated a corresponding amount and consequently the phase of the voltageA induced in its single phase rotor winding Vis advanced or retarded, dependent upon the direction-oil the rotation.- Asthe movement of the longitudinal feed continues;` the signal which is Yrecorded y instant vso that there is". y recorded on the tape a pattern of varying Vphase' a` reference alternating" phase of the voltage varies from instant to relationships between voltage .and a signal alternating'voltage'which represents the position of the tool from instant to instant Aon,` the axis ofthe longitudinal feed.

Similarly, as the position Aof the tool changes along the axis of the cross-feed, the phase of. the

voltage induced in the rotor winding ofthe rotary induction device Il is advanced or retarded, de-

from the storage reel 89 past the record and play` back head andwound uponthe take-up reel 90.

Alternating voltages will now be induced in the coils 50, 54 and 58, in accordance with the voltages which were previouslyl recorded. The 400 cycle reference voltage which is induced in the coil 50 is amplied by the preamplifier 80 and is supplied vto the input of the Selsyn exciter and amplifier unit I2. The three phase output voltage of this unit is supplied to the three phase stator windings of the longitudinal and crossfeed rotary induction devices Il and I0, respectively.

'I'he phase of the voltage induced in the rotor winding of the cross-feed rotary induction device represents the present'instantaneous position of the tool on vthe cross-feed axis. This signal voltage is supplied to one input circuit of the crossfeed phase discriminator 11. At the same time, a signal voltage is induced in the coil 58, in accordance with lthe recorded cross-feed signal voltage. This signal voltage which is induced in the coil 58 is amplified by the preamplier 82 and the amplified voltage is supplied to the second input of the cross-feed phase discriminator 11.

` The phase of this voltage at each instant represents the recorded or the desired position of the tool on the cross-feed axis at that instant.

'Ihe cross-feed phase discriminator 'I1' com-` pares the phases of these ktwo signal voltages which are supplied to its input circuits.l As previously explained, the output of the phase discriminator 11 is a direct voltage which is propor` tional to the phase error between the desired and the present position signal voltages. At any instant in which 'the tool isin the desired position on the cross-feed axis, the output voltage of the phase discriminator shouldfbel zero so that zero voltage shall be supplied to the cross-feed motor 8. However, the output voltage of the'phase discriminator is vzero.only when the input voltages are displaced from each other 90 degrees in phase.

To produce this required 90 degree phase displacement when the tool is in the desired inr stantaneous position on the cross-feed, a phase shifting device 92 is included in the connections.'

38. It is preferably-a three phase differential Selsyn device, i. e. it has a distributed three phase f vstator winding and a distributed threephase rotor winding. At' the Abeginning of the playback operation the rotor member is rotated suf'- ciently to displace the voltage supplied from the rotor winding of the rotary induction device Il to pending on the direction of the movement of the l` tool. As the movementcontinues, the phase 'of the Vcross-feed voltage signal which is recorded Aon the tape varies with respect to the recorded reference Y voltage so that la pattern is recorded tool is in the desired instantaneous cross-feedv of varying phase-relationships between areference alternating voltage and `a signal alternatone input of the phasel discriminator 11, de'

supplied to the inputs of the phase discriminator will be 90 degrees out of phase, the output volt- =age Voi' the discriminator Lwill be zero and the cross-feed motor 8 will be at standstill when the position. f

As the tape passes through the recording head the phase of the voltage induced in coil U8 will `of the change, i. e. an increase or decrease in the 90 degree relationship. Responsively to this output voltage the motor 8 is energized for rotation in a direction to reduce the error in the position of the tool and simultaneously to rotate the rotor of the rotary induction device I I to restore the 90 degree relationship of the input voltages which exists when the present position of the tool coincides with the desired position. Ali though this position correcting operation is described as a single step taking place in an instant of time, it is actually in continuous progress during the playback operation. rIhus by tending to reduce the error at all times, the system causes the tool to follow the same cross-feed motions that were recorded.

The correct positioningof the tool in the longitudinal direction is accomplished in a. similar manner. induced in the rotor Winding of the rotary induction device I and supplied to one input circuit of The present position signal voltage is the longitudinal phase discriminator 59 and the f recording in the longitudinal channel of the tape induces in the coil 54 a signal voltage which represents the desired longitudinal position of the tool. It is amplified by the preamplifier B3 and supplied to the other input of the phase discriminator 59. The manner in which the corrections in the longitudinal position of the tool are made in successive instants of time is ideni tical with that described for the cross-feed and a repetition of the described operation is therefore omitted.

Thus, the tool is continuously positioned along the cross and longitudinal feeds, following the same program of motion that was recorded. The result is a piece of work that is identical to the first piece which was made by manual control of the lathe. It is not essential that the reference voltage and the signal voltages from the longitudinal and cross-feed Selsyns III and II be simultaneously recorded. For many operations it may be desirable to pre-record the reference voltage signal from the oscillator and subsequently to record the signal voltages from the Selsyns in correct relationship with the pre-recorded reference voltage. This is accomplished by separating the movable contacts S1 to S1 of the record and playrecording head in the direction of the arrow and the 400 cycle reference voltage is recorded in the reference channel by the recording head coil 50.

After this recording is complete, the tape is rewound and the switches S1 to S7 are operated to the positions indicated by the chart for condition No. 2, program recording, and the tape is again passed through the recording head in the direction of the arrow. Under this condition, it will be noted that the coil operates as a pick-up coil with the result that a 400 cycle voltage is induced therein and through the preampliiier 8U to the input circuit of the Selsyn exciter amplifier 4I2 in which it is converted into three phase voltage and supplied through the phase shifting device 92 to excite the stator windings of the longitudinal and cross-feed Selsyns I0 and II. The vo'tages derived from the secondary windings of these Selsyns are passed through their respectiveV record circuits 52 and 56 and are recorded on the tape by recording head coils 54 and 58, respectively. During this time, of course, the longitudinal and cross-feed drive motors 'I and 8 are being manually controlled through the -master control station to cause the tool 5 to cut the workpiece d to the desired shape and dimensions, as explained at a previous point inthe specication. At the completion ofthe program to be recorded, the magnetic tape isagain rewound in preparation for the playback operation.

For the playback operation the switches .Si to S1 are operated to the positions indicated by the chart for condition No. 3, program playback, and the tape Ais again passed through the recording head in the direction of the arrow. Under this condition the recording head coils 50, 54 and 5a all operate as pick-up coils. The voltage induced in the coil 50 is supplied to .the Selsyn exciter amplifier to excite the stator windings of the longitudinal and cross-feed Selsyns and the voltages inducedin the coils 54 and 58 are supplied through their respective preampliiiers 83 and 82 to corresponding input circuits of the longitudinai and cross-feed phase discriminators 58 and 'I1 and the voltages derived from the secondary windings of the Selsyns I0 and I I are supplied to the second input circuits of the discriminators to effect control of the motors 1 and 8 to reproduce the recorded operations, as described at a back switch and operating them to the positions mi dened by the following chart:

-previous point in the specification. 'Y

It` wil be noted that the 400 cycle oscillator is used onlyunder condition No. 1, reference recording. If the reference voltage is recorded at the time of manufacture of the tape or at. any time prior to recording a w'ork program, the 400 cycle oscillator may be omitted from the control equipment.

f Another possibility is to supply a 60 cycle voltage to the recording head coil 50 and to drive the tape at 6%00 of its normal speed to record the reference voltage. Then under the program recording and playback conditions the tape would Switch Contacts S1 S; S4 S; Sg S1 Condition No. l. Reference Recording.... R Open Open R .v Ogen Open Open Condition N o. 2, Program Recording P R R Open R R Condition No. 3, Program Playback.. P P P Open P P P .be run at normal speeds andthe desirable effect of the 400 cycle reference voltage would be obf tained.

Although in accordance with the provisions oi the patent statutes this invention is described position, the magnetic tape is run through the as embodiedy in concrete form and the principle thereof'has been explained together with the best mode in which it is now contemplated applying that principle, it will be understood that the elements shownand described are merely illustrative and that the invention is not limited thereto since alterations and modifications will readily suggest themselves to persons skilled in the art without departing from the true spirit of this invention or from the scope of the annexed claims. v

What we claim as nwand desire to secure by Letters Patent of the lUnited States is:

1, A programming control system comprising i mans for reproducing two single phase alternating voltages from a record of two'alternating voltages, one of said reproduced voltages being a reference alternating voltage of substantially constant frequency and the .second reproduced voltage having a variable phase relationship with respect to said reference voltage, a movable load object, an electric motor coupled to drive said load object, a rotary induction device having a rotor member coupled to said load object and a stator member, a three phase distributed primary winding on one of said members, a single phase secondary winding on the otherof said members, an amplifier having a single phase input circuit anda two phase output with the output voltages in quadrature, and a Scott connected transformer having its two phase primary winding connected to said two phase output and having its three phase secondary winding connected to said three phase primary winding of said .rotary induction device, connections from said reproducing means to said input circuit of said amplier for supplying said reference voltage thereto and causing to be supplied to said primary winding of said induction device a three phase voltage of corresponding frequency. an electronic phase discriminator having two input circuits and a direct voltage output with the direct voltage varying in magnitude with variations in the phase relationship of the input voltages and changing in response to opposite departures from a predetermined polarity phase relationship of said input voltages, connections from said reproducing means'to one of said discriminator input circuitsv for supplying lsaid second alternating voltage thereto, connections from said secondary winding of said rotary induction device to the other of said discriminator input circuits for supplying thereto a single phase alternating'voltage varying in phase' with respect to said reference voltage in response to movements of said load object, and an amplidyne generator having its armature connected to the armature of said motor and having its control field windings excited in response tothe output voltage of said discriminator to control said motor to move said load` object and to rotate said rotor member in a direction to restore said predetermined phase relationship between the voltages supplied to said input circuits of said discriminator.

2. A programming control system comprising a magnetic recording and playback tape, iirst and second recording and playback head coils cooperating therewith, a source of alternating voltage and connections from said source to said first coil fo-r causing said coil to record a reference voltage on said tape, a movable load object, a rotary induction device having a rotor member connected to said load object and a stator member, a primary winding on one of said members and a secondary winding on the other of said members. connections from said source for supplying an alternating voltage to said primary winding, connections from said secondary winding to said second coil to provide for recording on said tape an alternating voltage having a phase relationship to said reference voltage varying with movements of said object, a phase discriminator having two input circuits and a direct voltage output circuit with the direct voltage changing in polarity in response to opposite de partures from a predetermined phase relationship of the input voltages and varying in magnitude with variations in the phase relationship of said input voltages, switching means for disconnecting said 'primary winding and said coil from said source and said second coil from said secondary winding and for connecting said rst coil to said primary winding and said second coil and said secondary winding to respective input circuits of said discriminator, and driving means responsive to the direct voltage output of said discriminator for moving said object in a direction to restore said predetermined phase relationship of the voltages supplied to the input circuits of said discriminator.

3. A programming control system comprising a magnetic recording and playback tape, first and second recording and playback head coils arranged in cooperative relationship with said tape, a source of single phase voltage, connections from said source to said iirst coil to provide for recording a reference voltage on said tape, a movable load object, a rotary induction device having a rotor member connected to said load object and a stator member, a three phase winding on one of said members and a single phase winding on the other of said members, an amplifier unit having a single phase input supplied from said source, a two phase output and a Scott connected transformer having a two phase primary winding connected to said two phase outputand a three phase secondary winding connected to said three phase windingof said induction, device, connections from said single phase Winding to said second coil to provide for recording on said tape a voltage having a phase relationship with said reference voltage varying with movements of said objzct, a phase discriminator having two input circuits and a direct voltage output circuit with the direct voltage changing in polarity in response to opposite ,o

departures from a predetermined phase relationship of the input voltages and varying in magnitude with variations in the phase relationship of said inputvoltages, switching means for disconn'cting said amplifier and said rst coil from said source and said second coil from said single phase winding and for connecting said rst coil to the input of said amplier and said second coil and said single phase winding to respective input circuits of said discriminator, and driving means responsive to the direct Voltage output of said discriminator for eiecting a movement of said object to a position in which the oltages supplied to the input circuits of said disy criminator are in phase.

4. A programming control system for recording and reproducing movements of an object comprising a magnetic recording and playback tape having iirst and second recording and playback head coils cooperating therewith, a source of single phase voltage connected to said rst coil to Provide for recording a reference voltage on said'tapB, a movable object, a rotary induction device having a rotor member connected to l5 said object and a stator member, a three phase winding on one of said members, a single phase winding on the other of said members, an ampliiler unit supplied from said source and having a two phase output and a Scott connected transformer having a two phase primary winding connected to said two phase output and a. three phase secondary winding connected to said three phase winding of said induction device, connections from said single phase winding to said second coil to provide for recording on said tape a voltage having. a phase relationship with said reference voltage varying with movements of said object. a phase discriminator having two input circuits and a direct voltage output circuit with the direct voltage changing in polarity with reversal in the phase relationship of the input voltages and varying in magnitude with varia.- tions in the phase relationship of said input l voltages, switching means for disconnecting said amplifier and said ilrst coil from said source and said second coil from said single phase windausvmo ing and for connecting said ilrst coil to said input of said amplifier and said second coil and said single phase winding to respective input circuits of said discriminator, and driving means including an electric motor responsive to the magnitude and polarity of said direct voltage for driving said object toward a position in which the voltages supplied to said input circuits of said discriminator are in phase.

ORRIN W. LIVINGSTON. LAWRENCE R. PEASLEE.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date Re. 16,667 Hewlett et al July 5, 1927 2,459,253 Tyrner Jan. 18, 1949 2,475,245 Leaver et al July 5, 1949 

